Practicing Spec-Driven Development - End-to-End Code Generation from Requirements to Implementation with Kiro
Control AI agent output quality through a three-stage spec workflow of requirements, design, and tasks to generate code that matches your intent. This article explains the structure of spec files and effective writing patterns.
What Is Spec-Driven Development?
Traditional AI coding tools center on chat-based interactions and code completion, responding to developer instructions one step at a time. This approach works well for small tasks, but when developing features that span multiple files or making architectural changes, the AI struggles to grasp the big picture and tends to generate inconsistent code. Kiro's spec-driven development addresses this challenge. When a developer describes requirements in natural language, Kiro (1) organizes functional and non-functional requirements in a requirements document (requirements.md), (2) defines the architecture and data flow in a design document (design.md), and (3) breaks down implementation steps in a task list (tasks.md). These three documents serve as the AI agent's "specification," and each task is executed in order to generate code.
Rule Control with Steering Files
Steering files are a mechanism for communicating project-specific rules and policies to the AI. They are placed as Markdown files in the .kiro/steering/ directory and describe coding conventions, architectural policies, libraries to use, prohibited practices, and more. For example, you can define rules like "Always enable TypeScript strict mode," "Use Zustand for state management and do not use Redux," or "Always validate API responses with Zod." Steering files have an inclusion setting that lets you choose from always (always loaded), fileMatch (loaded only when matching a specific file pattern), or manual (loaded only when manually specified). Global steering (~/.kiro/steering/) applies to all projects, while workspace steering (.kiro/steering/) is used for project-specific rules.
Agent Hooks and Sub-Agents
Agent hooks are a feature that automatically runs processes triggered by specific events such as file saves or Git commits. For example, you can define workflows that run ESLint and auto-fix on every TypeScript file save, or run tests on commit and abort the commit if they fail. Sub-agents are specialized agents that operate in an independent context from the main agent. They can split complex tasks and run in parallel when file sets are independent. For instance, you can simultaneously work on backend API implementation and frontend component implementation. The planner agent is a special read-only agent that specializes in breaking down requirements and formulating implementation plans. It verifies design validity before implementation and detects oversights and contradictions in advance. For a systematic study of AI code generation from basics to advanced topics, books on Amazon are a great resource.
Integration with Steering Files
Steering files (.kiro/steering/) work complementarily with specs. While specs define the specification for individual features or bug fixes, steering files define coding conventions, design policies, and quality standards that apply across the entire project. Three inclusion levels - always (always loaded), manual (loaded on demand), and fileMatch (loaded on file pattern match) - optimize context consumption while ensuring the right rules are applied. Since steering file rules are automatically referenced during spec task execution, code is generated with consistent quality.
Summary - Guidelines for Spec-Driven Development
Kiro's spec-driven development improves the quality and consistency of AI coding by advancing from requirements to implementation through a structured workflow. By making project rules explicit with steering files and automating quality checks with agent hooks, you can continuously ensure the quality of AI-generated code. We recommend starting with a small feature addition to try spec-driven development and gradually enriching your steering files over time.